Web drawing devices are employed in printing presses for conveying the start of a web of material along a desired draw-in path through the printing press. This is required, for example, for a draw-in in connection with a new production. This is also always required in the case where a web of material was torn during the printing process, because then the start of the new web of material cannot be pulled through in the manner of a flying roll change. Furthermore, in modern printing presses the printing groups can be reached by the web to be printed along different conveying paths in order to be able to obtain correspondingly different printing results. In case of a change-over in the conveying path, the fresh web of material must be drawn in along the appropriate draw-in path.
A device for drawing a web of material into a processing station is known from DE 94 15 859 U1. The draw-in mechanism, which is in the shape of a tape, can be rewound from a winding roll at the inlet of the processing station to a winding roll at the outlet of the processing station.
A device for drawing webs of material into rotary printing presses is known from DE 22 41 127 A1. The draw-in mechanism, which is embodied in the form of a spring steel strip, can be pushed from the outlet of the printing press along different draw-in paths, between which switching can be performed by the use of shunts. In this case, the draw-in mechanism is driven by a stationarily arranged drive wheel, which drive wheel comes into positive contact with the draw-in mechanism and pushes the draw-in mechanism along its entire length through the printing press.
EP 0 418 903 A2 discloses a device for drawing in a web of material. A draw-in mechanism is driven by a motor which is controlled as a function of measured data obtained in the draw-in process. Control is performed with a view to a constant draw-in speed, or to a constant number of revolutions.
A device for drawing in a web of material is disclosed in DE 94 09 390 U1. A draw-in mechanism is driven by a step motor. A conveying distance already traveled by the draw-in mechanism is detected by sensors.